Write a brief that makes the next decision easier.

Start with the decision, not the output file.

“We need an STL” describes a file. “We need to check whether the connector clears the enclosure wall” describes the work that file must support. The second statement gives the person reviewing the project a reason to ask about the connector, the mating part and the planned check.

The same distinction matters for a display model or animation. A display might need to show the relationship between two subsystems. A video might need to explain a three-step sequence. Naming the audience and the question helps keep decorative detail from becoming the entire brief.

Make the reference easy to identify.

List the file name, revision and unit system you intend everyone to use. If there are marked dimensions in a PDF, say whether they take priority over a rough sketch. If the design is not final, identify which interfaces are fixed and which can still change.

A screenshot can communicate appearance, but it usually cannot communicate every dimension needed for fabrication. Treat a missing dimension as an open question rather than asking another person to guess it from the image. The brief builder has a place for unresolved questions for exactly this reason.

Record what a calculation includes.

A cost estimate based on supplied machine time changes if the slicer later predicts a longer job. State whether setup is charged once per batch and whether the supplied material quantity includes supports. Keep the original inputs with the result so another person can follow the arithmetic.

For scale models, record the real-world units and the chosen ratio. An 8 m dimension at 1:25 becomes 320 mm. That calculation does not say whether a thin rail, label or moving feature can survive the same reduction. Those are separate design decisions.

For screens, distinguish content dimensions from display dimensions. A wide image placed on a narrower display can be cropped or letterboxed. Choose deliberately, then place essential labels inside the area that will remain visible. The physical screen dimensions from a diagonal calculation exclude its bezel and mounting hardware.

Agree on the check before the work starts.

State who will review the result and what they will look at. A fit prototype can have a different review method from a visual mock-up. An animation may need a script review before modelling and another review before final output. Recording the checkpoints makes it easier to distinguish a correction from a changed requirement.

Also record the handover: quantity, file formats, packing, delivery location and any setup requirements. A desired date is a planning input, not a confirmed production slot. Ask the supplier to confirm the schedule against the actual scope.

A short example: enclosure fit review.

This is an illustrative planning example, not a record of a completed customer job or a promise of capability. Its useful feature is that the unknowns remain visible.